1. Field of the Invention
The present invention relates to an image forming apparatus that has attached thereto a post-processing device that carries out post-processing a sheet on which an image is formed, and a sheet placing direction instructing method.
2. Description of the Related Art
Conventionally, image forming apparatuses, such as copying machines and laser printers, that permit insertion of colored sheets, OHP sheets, pre-printed sheets or the like into specific pages of an output bundle of sheets, are known (for example, Japanese Laid-Open Patent Publication (Kokai) No. 2000-295410). Moreover, image forming apparatuses are known that are capable of outputting only monochrome or black-and-white image sheets, and permitting insertion of color output sheets in an output bundle of sheets.
With these image forming apparatuses, it is possible to select among various modes, such as a cover sheet mode for inserting a sheet at the first page of a bundle of sheets, a back cover sheet mode for inserting a sheet at the last page of a bundle of sheets, or an interleaved sheet mode for inserting sheets between the first sheet and the last sheet in a bundle of sheets, so that a sheet can be inserted at any given page.
When inserting a sheet in such image forming apparatuses, one of a plurality of cassettes in which recording sheets are contained is designated as an exclusive insertion sheet cassette, in which insertion sheets such as cover sheets and interleaved sheets are contained. Recording sheets are supplied from cassettes other than the exclusive insertion sheet cassette when an insert page is not reached, and an insertion sheet is supplied from the designated exclusive insertion sheet cassette when the insert page is reached. Then, all the supplied sheets are conveyed to an image forming section. However, although images are formed on the recording sheets, no image is formed on the insertion sheet.
Moreover, when inserting a sheet using a different method, an inserter is disposed at a discharge port of the image forming apparatus. The inserter is provided with a cassette that contains insertion sheets. Then, the inserter receives from the image forming apparatus recording sheets on which images have been formed and inserts a sheet, such as a cover sheet or an interleaved sheet supplied from a cassette inside the inserter, between given pages of the recording sheets, after which a bundle of sheets with the insertion sheet inserted therein, is output from a discharge port (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. 2000-295410).
Moreover, a finisher (sheet processing device) is also known, which is connected to the image forming apparatus, for aligning, aligning, and binding or stitching sheets, and which, when provided with a cassette, also functions as an inserter.
Further, an image forming apparatus is known, which temporarily stores an image in a memory and rotates the image to match the sheet size and sheet orientation, after which it forms the image on the sheet (Japanese Laid-Open Patent Publication (Kokai) No. S62-213372). By combining the image rotation processing with post-processing such as binding, it becomes possible to perform post-processing at any given position on a sheet that cannot be post-processed except at a preset position vis-à-vis the image forming apparatus.
However, with the conventional image forming apparatus and sheet processing device described above, if sheet insertion processing and post-processing are performed, when image rotation is performed to match a specified post-processing position, the orientation of the sheet on which the image is formed and the orientation of the inserted sheet sometimes do not match.